15,091 research outputs found
Calculations, and comparison with an ideal minimum, of trimmed drag for conventional and canard configurations having various levels of static stability
Classical drag equations were used to calculate total and induced drag and ratios of stabilizer lift to wing lift for a variety of conventional and canard configurations. The Flight efficiencies of such configurations that are trimmed in pitch and have various values of static margin are evaluated. Classical calculation methods are compared with more modern lifting surface theory
A bright millisecond radio burst of extragalactic origin
Pulsar surveys offer one of the few opportunities to monitor even a small
fraction (~0.00001) of the radio sky for impulsive burst-like events with
millisecond durations. In analysis of archival survey data, we have discovered
a 30-Jy dispersed burst of duration <5 ms located three degrees from the Small
Magellanic Cloud. The burst properties argue against a physical association
with our Galaxy or the Small Magellanic Cloud. Current models for the free
electron content in the Universe imply a distance to the burst of <1 Gpc No
further bursts are seen in 90-hr of additional observations, implying that it
was a singular event such as a supernova or coalescence of relativistic
objects. Hundreds of similar events could occur every day and act as insightful
cosmological probes.Comment: 18 pages, 4 figures. Accepted by Science. Published electronically
via Science Express on September 27, 200
Analytical Model for the Optical Functions of Indium Gallium Nitride with Application to Thin Film Solar Photovoltaic Cells
This paper presents the preliminary results of optical characterization using
spectroscopic ellipsometry of wurtzite indium gallium nitride (InxGa1-xN) thin
films with medium indium content (0.38<x<0.68) that were deposited on silicon
dioxide using plasma-enhanced evaporation. A Kramers-Kronig consistent
parametric analytical model using Gaussian oscillators to describe the
absorption spectra has been developed to extract the real and imaginary
components of the dielectric function ({\epsilon}1, {\epsilon}2) of InxGa1-xN
films. Scanning electron microscope (SEM) images are presented to examine film
microstructure and verify film thicknesses determined from ellipsometry
modelling. This fitting procedure, model, and parameters can be employed in the
future to extract physical parameters from ellipsometric data from other
InxGa1-xN films
Clinical and laboratory studies of the bacterial pathogenesis and management of Pouchitis
20-50% of patients develop pouchitis following restorative proctocolectomy for ulcerative
colitis (UC). Pre-pouch ileitis (PPI) also develops in some of these patients.
Bacteria are implicated in the pathogenesis of pouchitis and antibiotics are the mainstay of
treatment. Studies were performed to examine the role of bacteria in the pathogenesis of this
disease and to develop new treatment. Further studies examined the prevalence and
implications of PPI and the efficacy and complications associated with maintenance
antibiotic therapy.
16s rRNA sequencing demonstrated an increase in Proteobacteria and a reduction in
Bacteroidetes in the UC compared with the familial adenomatous polyposis (FAP) cohort, but
only limited differences between the UC non-pouchitis and pouchitis groups. We were unable
to identify an individual species or phylotype specifically associated with pouchitis.
Treatment with elemental diet produced a symptomatic improvement in 71% of chronic
pouchitis patients but none entered clinical remission.
Patients with PPI were identified, the prevalence, symptoms and short term outcomes of this
group were studied. PPI was identified in 5.7% of patients with UC. All patients had
associated pouchitis but not all were symptomatic. PPI was not associated with
reclassification to Crohn’s disease. A subgroup of patients with symptomatic pre-pouch ileitis
were treated with combination antibiotic therapy and 86% entered remission.
Faecal samples from patients with antibiotic resistant pouchitis were grown on agar and
sensitivity patterns identified. Following guided antibiotic therapy 80% of patients entered
remission. Stool analysis also identified the presence of extended spectrum beta-lactamase (ESBL) resistant coliforms in 35% of patients with chronic pouchitis. Not all were
symptomatic. PPI was associated with an increased risk of ESBL.
Patients treated with maintenance antibiotic therapy were identified. Pre-pouch ileitis was
associated with an increased risk of relapse. Reported side effects were rare and treatment
was associated with an improved quality of life
Asymptotics of the partition function for random matrices via Riemann-Hilbert techniques, and applications to graphical enumeration
We study the partition function from random matrix theory using a well known
connection to orthogonal polynomials, and a recently developed Riemann-Hilbert
approach to the computation of detailed asymptotics for these orthogonal
polynomials. We obtain the first proof of a complete large N expansion for the
partition function, for a general class of probability measures on matrices,
originally conjectured by Bessis, Itzykson, and Zuber. We prove that the
coefficients in the asymptotic expansion are analytic functions of parameters
in the original probability measure, and that they are generating functions for
the enumeration of labelled maps according to genus and valence. Central to the
analysis is a large N expansion for the mean density of eigenvalues, uniformly
valid on the entire real axis.Comment: 44 pages, 4 figures. To appear, International Mathematics Research
Notice
Turbulence measurements in a swirling confined jet flowfield using a triple hot-wire probe
An axisymmetric swirling confined jet flowfield, similar to that encountered in gas turbine combustors was investigated using a triple hot-wire probe. The raw data from the three sensors were digitized using ADC's and stored on a Tektronix 4051 computer. The data were further reduced on the computer to obtain time-series for the three instantaneous velocity components in the flowfield. The time-mean velocities and the turbulence quantities were deduced. Qualification experiments were performed and where possible results compared with independent measurements. The major qualification experiments involved measurements performed in a non-swirling flow compared with conventional X-wire measurements. In the swirling flowfield, advantages of the triple wire technique over the previously used multi-position single hot-wire method are noted. The measurements obtained provide a data base with which the predictions of turbulence models in a recirculating swirling flowfield can be evaluated
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